Present day flexible ducting is constructed using rubber, fabric reinforced rubber (for example, flexible ducts available from RCF Technologies, Inc., Vidalia, Ga., www.rcftechnologies.com) or flexible plastics secured to metal or rigid tubing by means of commercially available band clamps or welding. Sealing against fluid as well as against internal or external pressure and slippage are important functions of the clamp.
One typical type of band clamp consists of a metal strip with helical slots at one end. The slots slip through a worm gear located at the opposite end. The strip is wrapped around a tubular end section of the duct which has been placed over a beaded metal tube to which it is secured. The strip is fed through the worm gear and tightened until the duct is locked in place and sealed. Where higher pressures are involved, the duct may, in time, slip out from under the clamp. Hence, a bead is provided at the end of the tube to act as a stop.
As the band or strip is drawn through the worm gear and tightened, friction between it and the duct material causes the duct material to move with the strip and gather near the worm gear. This can create a leak path and many designs of band clamps have been developed to address this problem, with varying degrees of success.
It would be desirable to have a duct sealing system that would adequately address the problem of slippage and leakage. Furthermore, it would be desirable to have a sealing system that would not require manual tightening.